Basic Information
Name	Xi-26
Launch date:	18 September 2021
Rocket description	- 76.2 aluminum airframe - 4 motor-mounted fins, 2024 aluminum - 3D printed conical PLA nosecone - 3 ft. ellipsoidal "Fruity Chutes" parachute
Payload	- Raven3 altimeter (primary role) - Eggtimer Classic altimeter for backup apogee separation and backup main deploy - BREO-N flight computer (2^nd backup, apogee only) - BRB900 GPS transmitter - Liftoff-activated and apogee-activated smoke trackers with Legendary formulation. - SJCAM C100+ mini-camcorder, side-facing
Liftoff mass	3.723 kg.
Stability Margin (minimum)	2.05
Flight objectives	- 2^nd flight powered by APM-G motor with a single BATES grain of KNPSB propellant. -test new minicamcorder

Motor details
Motor name	APM-G
Propellant	KNPSB (potassium nitrate/potassium perchlorate/sorbitol)
Grain mass	460 grams
Nominal impulse	657 N-sec.
Class	I

Additional information

- For this flight, motor has enlarged throat to operate at lower pressure for extended burn time. To facilitate startup, a 3/16” diameter restrictor fitted into throat as part of igniter system.

- The APM-G motor serves as aft airframe. Four fins are attached to the motor with lugs and collars mounted in through-holes fore and aft of the combustion chamber.

- New SJCAM C100+ minicamera is HD and is configured to be side facing (no mirror) for this flight. The camera is mounted in an auxilliary bay situated between the motor and mid-body sections of the rocket.

- For this flight, the liftoff-actuated smoke module is mounted in the mid-body section. Usually it is mounted in the aft-body section that houses the rocket motor.

Weather conditions
Temperature	26°C (79°F)
Wind	SSW 30 km/hr gusting to 50 km/hr
Sky	Clear with bright sun
Other	scattered clouds (cirrus)
Ceiling	unlimited

Launch Event Description

Following our checklist, we proceeded to set up the rocket. Setup went well with no glitches. The BRB transmitter and receiver were activated and verified that a good GPS signal was obtained. The BREO was activated and verified to be functioning, followed by the EggTimer unit and Raven. Raven beeped out codes indicating nine volts battery power and three active pyros. The on-board camera was then powered up. The lift-off activated smoke charge was then powered.

For videotaping the flight, I used my Sony HDR-CX240 Handycam fitted with scope tube. Additionally, a close-up HD video camera was mounted on a tripod a short distance from the launch pad.

After verifying the sky was clear, the countdown proceeded. At the zero mark, the ignition button was pressed, the igniter fired immediately. Smoke was seen issuing from the rocket motor and continued for about two seconds. The rocket then rapidly accelerated off the pad. Just before clearing the launch rod, the motor suddenly CATOed with a loud report. Small pieces of debris were seen to scatter, while the main section of the rocket was seen to fly upward on a ballistic trajectory, estimated to be a few hundred feet at apogee. As the rocket descended, the pyro charges were heard to fire. The parachute, however, was not seen to deploy. The rocket tumbled earthward and landed in tall grass 200-300 feet downwind of the launch pad. Smoke was seem emanating from the rocket after it landed, clearly, the smoke charge(s) had successfully ignited. I immediately headed toward the landing site, using the smoke to pinpoint the exact location.

Simultaneous to the rocket falling, the burning grain of propellant was seen descending, trailing smoke as it fell. It appeared to burn out a couple of seconds after hitting the ground.

Arriving at the touchdown site, most of the rocket components appeared to be present (except, of course, the motor section) and damage to the forward section of the rocket seemed minimal. All the pyro charges had fired with the exception of the BREO backup apogee pyro. Both the liftoff-actuated and apogee-activated smoke charged had burned. The nosecone had broken upon impact, spilling out the BRB unit onto the ground. The AvBay looked to be undamaged. Only the auxilliary bay, which housed the camera, appeared ‘beat up’, and the camera was not present. The parachute was no where to be found.

Near the launch pad, the motor casing (less the four fins) and nozzle were found. Failure due to overpressurization was apparent, as the forward snap ring groove had failed in tension. The nozzle was undamaged.

Flight Analysis
Event:	Time (sec)	feet	metres
Apogee	4.8	266	81
Separation	5.2	246	75
Main deployment *	5.2	246	75
Touchdown	9.6	-	-
Range	-	264	80
Descent rates:	ft./sec.	m/sec.
Free-fall	55	16.7
Main parachute *	-	-

* Chute pyros fired however chute did not deploy

Post-flight analysis and comments:

The version of the APM-G motor used for this flight had been successfully static fired prior to the flight, performing nominally. It was originally thought that the motor failure was a result of using a flow restrictor ( 3/16” (5mm) wooden dowel, which formed part of the motor igniter, inserted into the nozzle throat to facilitate motor startup). A few months after the flight, I found the propellant grain that was intended to be used for the flight motor (misplaced in the grain storage container). The grain that was used, and caused the failure, was a rejected grain that was not properly labeled. While demoulding the grain, it was found that the coring rod was very tight and attempts to remove it caused the grain to crack through the web. The increased burning area due to the crack, combined with a structurally compromised grain, was clearly responsible for the CATO. Lesson learned, in the future rejected grains must be prominently marked as such, or discarded.

All the electronic components were carefully inspected. No damage was apparent. Testing indicated nominal operation. Flight data was successfully downloaded from the Raven and EggTimer. All pyro charges had fired nominally, except the BREO apogee pyro. It is speculated that the power to the BREO was momentarily interupted during the CATO event (to be confirmed).

The forward and mid body sections were in good condition, having only minor dents that are readily repairable. The on-board camera and parachute were not recovered.

Although the parachute was apparently deployed during descent, it was not spotted, nor found after an exhaustive search. It may have been carried off by the wind, which was blowing strongly at the time (30 km/hr gusting to 50 km/hr). There was no sign of overload to the attachment point of the rocket. After much deliberation, it was concluded that the parachute was very likely not attached to the rocket during packing. Somehow I had failed to attach the parachute’s quick-link to the eyebolt on the parachute piston. As there are a total of seven tethers and seven attachment points, it is indeed feasible to miss something eventually, and this is apparently what happended. For future flights, a checklist will be used to ensure all connections are correctly made. In retrospect, it may have been fortuitous that the motor failed on this particular flight, else, with the chute not attached, the rocket would have free-fallen all the way to the ground. This would likely have caused more damage, in particular to the electronics, than was the case.

Raven data:

Barometric and axial acceleration data Xi-26\Xi-26_Raven-basic.jpg

Eggtimer data:

Altitude versus flight time Xi-26\Xi-26_ET.jpg

Miscellaneous photos:

APM-G rocket motor (for static test) Xi-26\APM-G.JPG

KNPSB propellant grain Xi-26\KNPSB-grain-APM-G.JPG

Launch photos:

Rocket on pad Xi-26\2021-09-22_16-51-18.jpg

Motor beings to burn Xi-26\2021-09-22_16-52-19.jpg

Xi-26\2021-09-30_15-45-36.jpg

Liftoff…! Xi-26\2021-09-22_16-52-46.jpg